title: Multiple regression analysis of factors predicting mycophenolic acid free fraction in 91 adult organ transplant recipients.
abstract: BACKGROUND
  Mycophenolic acid (MPA) is an antirejection drug used in various types of solid organ transplants. MPA is extensively bound to albumin, and free MPA is thought to be the primary immunosuppressive agent. Little is known of what contributes to the wide interindividual variability in the observed MPA free fraction (MPAf) in humans. The purpose of this study was to determine, using multiple regression analysis of demographic and laboratory variables that are routinely collected during clinic visits, patient factors that predict MPAf in a large sample (n = 91) of organ transplant recipients.
  
  
  METHODS
  Age, weight, height, total daily MPA dose, albumin, serum creatinine (SrCr), and MPAf were obtained from islet (n = 16), kidney (n = 28), and heart/lung (n = 47) transplant recipients. Multiple linear regression analysis and the The Spearman rank correlation were conducted using SigmaStat (version 3.5 for Windows). Significance was set a priori at P = 0.05.
  
  
  RESULTS
  The pooled data can be described as (mean ± SD) follows: age (52 ± 13 years), weight (72 ± 15 kg), height (169 ± 9 cm), total daily MPA dose (1632 ± 667 mg), albumin (42 ± 7 g/L), SrCr (112 ± 34 µmol/L), and MPAf (2.9% ± 3.5%). Multiple regression of all commonly acquired variables generated the following equation: MPAf = 1.865 + (0.0357 × age (yrs)) + (0.0125 × weight (kg)) - (0.0202 × height (cm)) - (0.000323 × total daily dose (mg)) + (0.0122 × albumin (g/L)) + (0.0160 × SrCr (µmol/L)) (r = 0.06), but none of the variables were significant predictors of MPAf (P > 0.05). The Spearman rank correlation of each individual variable confirmed lack of significant correlation with MPAf.
  
  
  CONCLUSIONS
  To our knowledge, this is the first study attempting to describe factors predicting MPAf in adult organ transplant recipients involving a large sample size. The novel findings of lack of significant predictors warrant further investigations using additional patient factors.
authors.affiliation: *Faculty of Pharmaceutical Sciences, The University of British Columbia; †Child and Family Research Institute; and ‡Department of Pharmacy, Children's & Women's Health Centre of British Columbia, Vancouver, British Columbia, Canada.
authors.forename: Tony K L
authors.initials: TK
authors.lastname: Kiang
authors.forename: Karen
authors.initials: K
authors.lastname: Ng
authors.forename: Mary H H
authors.initials: MH
authors.lastname: Ensom
mesh_terms: D000328:Adult; D000368:Aged; D016903:Drug Monitoring / Q000379:methods*; D005260:Female; D006801:Humans; D007166:Immunosuppressive Agents / Q000493:pharmacokinetics*; D016014:Linear Models; D008297:Male; D008875:Middle Aged; D015999:Multivariate Analysis; D009173:Mycophenolic Acid / Q000493:pharmacokinetics*; D016377:Organ Transplantation; D012189:Retrospective Studies; D018401:Sample Size; D018709:Statistics, Nonparametric
chemical_list: D007166:Immunosuppressive Agents; D009173:Mycophenolic Acid